1. Technical Field
The present invention relates to a sheet supply device for supplying print sheets (print media).
2. Background Arts
Conventionally, known is a sheet supply device that picks up a print sheet from a sheet supply tray and feeds the print sheet to a print unit by its registration rollers. In the sheet supply device, the print sheet is stalled in a state where its leading edge is contacted to a registration nip between the registration rollers to form a slack in the print sheet, so that an oblique feed of the print sheet can be compensated. Then, the registration rollers are driven to feed the print sheet to the print unit.
When the print sheet is fed forward by the registration rollers, the slack of the print sheet is expanded (i.e. back tension is applied to the print sheet) between the registration nip of the registration rollers and rollers located upstream from them. As a result, a noise (sheet expansion noise) may be generated due to the expansion of the slack.
A Japanese Patent Application Laid-Open No. 2010-215389 (Patent Document 1) discloses a sheet supply mechanism that also carries out an assistant operation. In the assistant operation, rollers located upstream from registration rollers are driven while the registration rollers are driven.
In the sheet supply mechanism, when supplying a print sheet form one of sheet supply trays disposed at a lower portion of a printer, the print sheet picked up from the one of the sheet supply trays is fed forward and then received by a pair of intermediate feed rollers. Then, the print sheet is stalled in a state where its leading edge is contacted to a registration nip between registration rollers by the pair of intermediate feed rollers to form a slack in the print sheet and then the rotation of the pair of intermediate feed rollers is stopped. Subsequently, the assistant operation is carried out by starting to drive the pair of intermediate feed rollers at the same time as starting to drive the registration rollers. According to this assistant operation, the print sheet is fed forward further by the registration rollers and the pair of intermediate feed rollers while the slack is kept.
By the above-explained assistant operation in the sheet supply mechanism of the Patent Document 1, the sheet expansion noise generated due to the expansion of the slack is reduced by keeping the slack amount of the initially-formed slack until a trailing edge of the print sheet passes through the intermediate feed rollers.